Crossbow trigger with improved sear surface and adjustment with ability to control trigger pull weight with various input draw weights

ABSTRACT

A crossbow trigger assembly with improved sear surface and reduced friction sear-engaging system. The trigger pull force can be adjusted through the use of a spring pocket that has a threaded insert in it allowing varying tension adjustment. An auto-safety feature consists of a pin that is forced rearward when trigger assembly is cocked, pushing the safety latch to the safe position.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Provisional Patent ApplicationNo. 61/855,605 filed May 20, 2013 by Derrick J. Middleton and titled“Crossbow trigger with improved sear surface and adjustment with abilityto control trigger pull weight with various input draw weights”.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to trigger mechanisms, and morespecifically, to a trigger device for a crossbow.

2. Description of the Related Art

Crossbows have long been known in the archery field for use in huntinggame. Crossbows have higher draw weights than conventional archery bowsand fire arrows (or “bolts”) with greater speeds. It is a function of acrossbow to have a lock or trigger mechanism that is able to hold thecrossbow string in the ready to fire position once the string is drawn.

When crossbows are configured for firing, the force exerted by theretracted bowstring can be in the range of approximately 100 to 400pounds. The trigger assembly of the crossbow must be capable of holdingthe bowstring in firing position, while allowing the bowstring to bereleased as the user pulls the trigger. This often results in anexcessive pull force which the user must exert upon the trigger of thecrossbow to fire the arrow, which in turn decreases the accuracy of theshot.

Typical trigger mechanisms known in the art use a metal to metal searmechanism which, during shooting, relies upon one flat metal surfacesliding across another flat metal surface, until their engagement breaksoff. In view of the substantial pressure exerted between these two flatengaged surfaces, the mating parts need be made of hardened steel toprevent rapid wear; in some cases, wear remains a problem, causinginconsistent trigger pressure and possible misfires. Furthermore, manyearlier devices lacked sufficient structure to provide positive,reliable safety means when handling the loaded crossbow.

A common configuration known in the art comprise trigger assemblies thatuse upward-opening claws (string retaining members) that hold the stringonce engaged, as seen for example in U.S. Pat. No. 4,877,008 (toinventor Troubridge), in which two flat metal engaging surfaces (sears)slide off each other upon the activation or depression of a trigger arm,releasing the upward-opening claw and firing the arrow.

One other commonly used trigger assembly utilizes a downward-openingclaw (string-retaining member); as exemplified by U.S. Pat. No.4,192,281 (to inventor King). In this system, the claw folds down belowthe string (thus releasing the string) when the trigger is activated;typically, “metal sliding on metal” is the method by which the two flatmetal engaging surfaces (sears) disengage.

In both of the above trigger actions (and, generally, in all triggersystems), trigger pull weight is the weight (or, more exactly thehorizontal force, expressed in lbs. force) required to physicallydepress the trigger and get the string to release. It is a function ofthese prior art crossbow actions that the trigger pull weight isaffected by the draw weight of the bow; for example, a 300 lbs. drawweight bow may require 4 lbs of trigger pull weight to get the string torelease; with a 150 lbs draw weight bow, the same action would requireless trigger pull weight (possibly 2 lbs) to get the bow to release thesame.

In the case of the two types of prior art trigger systems discussedabove, the manufacturers have tried to improve (reduce) trigger drawweight by polishing the engaging surfaces (or sear surfaces) forsmoother release. In some other cases, manufacturers reduced triggerdraw weight by reducing the overlap of the sear surfaces, which in turncauses an unsafe situation, because a heavier trigger and a heavier drawweight is utilizing less engagement area on the sears to achieve anacceptable trigger pull. It should be understood that these searsurfaces are prone to abrasive wear from the fact they engage each otherfrictionally with significant weight.

One other trigger mechanism known in the art, as exemplified by U.S.Pat. No. 4,693,228 (to inventors Simonds et al.) also uses a downwardopening claw, but one of the sear surfaces is replaced with a rotatingmember (a wheel), which engages a slightly curved second sear surface.While one would expect that a wheel would afford reduced friction, thuscausing a reduced trigger pull, the Simonds trigger mechanism stillexhibits a heavier trigger pull when paired with heavier input drawweights.

When studying the Simonds trigger, it was realized that its design isless efficient, despite the use of rotating means (wheel) to overcomefriction between the two sear surfaces. Because of its structural andfunctional design, the Simonds trigger has three points of contact(engagement under force) compared to two such points in the Troubridgeand. King patents discussed above. The three points of contact in theSimonds trigger assembly are: the trigger sear, the latch wheel searsurface, and the pin surface around which the wheel rotates. Friction,as we know, is the force that resists relative motion between two bodiesin contact. Rolling friction occurs when two objects move relative toeach other and one rolls on the other (like a car's wheel would roll onthe ground). This is classified under static friction because the patchof tire in contact with the ground, at any point while the tire spins,is stationary relative to the ground.

There is a need in the market, and a sought-after feature by crossbowmanufacturers, to have a trigger system that can be utilized on manyproducts with different draw weights, without the need for reconfiguringof the internal levers, toggles and such, that would allow the triggerpull weight to be kept relatively constant, even when paired withcrossbows with different input string weights. The above is importantbecause changing movement internally affects the function and engagementof various safety features that need certain clearances and would alsoneed to be altered based on any changed geometry.

It would be a further desirable feature to have a trigger that retains arelatively constant trigger pull distance, while keeping the triggerpull weight to a comfortable level, while also being easily to maintain.

It would be a further desirable feature to have a trigger with anauto-safety feature, whereby the safety latch would be automaticallyplaced in the safe position when the trigger assembly is cocked,blocking the possibility of trigger actuation without a further positiveaction by the user to switch the safety latch out of the safe position.

Lastly, there is a need in the market for a trigger assembly that uses arolling sear surface and two immediate points of contact, to trulyachieve a reduction in friction when two sear surfaces are engaged underforce.

SUMMARY OF THE INVENTION

It is an object of the present invention to overcome the shortcomings ofthe prior art, as described above. The present invention use a trulyreduced friction sear engaging system, a rolling sear surface and twoimmediate points of contact, to achieve and maintain a well-controlledand relatively constant trigger pull weight with various input bow drawweights. The improved crossbow trigger of this invention also allowsvarying input weights (bow draw weights) without changing the geometricfunction of the trigger assembly components.

It is a further object of this invention to allow manufacturers (andpossibly users) a degree of adjustability of the trigger pull or drawweight, by the use of an internal spring adjustment mechanism. Anotherobject of this invention is a trigger that is able to achieve mechanicaladvantage of internal components without the use of excessively longlever arms that often result in undesirable long trigger pull distance,commonly referred to as “trigger travel”.

The present invention uses a metal to metal sear mechanism, in which onesear is implemented as a rolling sear surface, namely a dowel mounted onoutward roller bearings, to reduce friction and maintain optimal searengagement at all times.

It is a further object of this invention to implement an auto-safetyfeature, whereby the safety latch is automatically placed in the safeposition when the trigger assembly is cocked, blocking the possibilityof trigger actuation without a further positive action by the user toswitch the safety latch out of the safe position.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a frontal view of a preferred embodiment of the presentinvention, in its locked position, ready for discharge, with half(front) of the housing removed to show the internal components;

FIG. 2 is a frontal view of a preferred embodiment of the presentinvention, in its after-fired position, with half (front) of the housingremoved to show the internal components;

FIG. 3a is a top view of the lower sear of a preferred embodiment thepresent invention;

FIG. 3b is a frontal view of the lower sear of a preferred embodimentthe present invention;

FIG. 3b is a perspective view of the lower sear of a preferredembodiment the present invention;

FIG. 4 is a top view of the two halves of the housing of a preferredembodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the invention in more detail, in FIG. 1 is a crossbowtrigger assembly of a preferred embodiment. FIG. 1 shows the trigger inits locked position which would have a string in the string retainingarea 1.d, ready for discharge. FIG. 2 is the same mechanism in theafter-fired position. In FIG. 1, components are housed in housing 1.i.,which is machined with cavity areas or pockets to accept the internalcomponents of the system. The claw 1.b pivots around the claw pivotpoint 1.a; the claw 1.b must pivot upwardly in order to fire. Thehousing 1.i includes an opening 1.c. in which the string enters, whilean area 1.d. is where the string is retained on the back side of thedownwardly facing claw 1.b. The housing 1.i further includes an area1.e. for receiving a spring which would bias the claw into an upwardposition, should it not have the string to force it to do the same. Onthe lower portion of the claw member 1.b is the upper sear surface 1.ffor the primary engagement of the input claw weight to the rest of thesystem. Further lower in housing 1.i is the lower sear pivoting point1.g, around which lower sear 1.h pivots. The housing 1.i is preferablymachined from an aluminum block, to accept all components. Anauto-safety pin 1.j is slidably mounted in a cylindrical channelmachined between the safety 1.k and the claw 1.b. When the claw 1.b iscocked with a string, the auto-safety pin 1.j is forced rearward, and,in turn, moves the safety 1.k into contact with rear portion of lowersear 1.h, placing the trigger in a safe position. The safety 1.k pivotsaround the safety pivot point 1.t. A trigger 1.u is attached to thelower sear 1.h.

FIGS. 3a , 3.b and 3.c are respectively a top view, a frontal view, anda perspective view of the lower sear of a preferred embodiment thepresent invention. In these figures, the lower sear 1.h is fitted withtwo wings 1 n.1 and 1 n.2. Each of these two wings has two bearingpockets 1.o.1 and 1.o.2, between which a dowel pin 1.p is rotatablyfixed. A threaded orifice 1.q is machined into 1.h to affix the triggerarm 1.u to lower sear 1.h.

FIG. 4 depicts the top view of the two halves of the housing 1.i, shownin exploded (apart) configuration. A spring pocket 1.l is machined intothe bottom of housing 1.i, providing biasing means (a spring) for lowersear 1.h to be pushed against, engage and hold upper sear 1.b when uppersear is moved to its loaded position. The spring pocket 1.l is threadedwith a blind set screw at the bottom portion; the screw has the abilityto be moved in and out, allowing tension adjustment of spring 1.n, thusallowing the trigger pull to be adjusted based on an incoming pressureof upper sear 1.b that may be 100 lbs. to 400 lbs.

As shown in FIG. 4, also machined into the bottom of housing 1.i is aset screw 1.m that allows the further adjustment of lower sear 1.h(impinging on wing 1.n.2), to enable proper angle of lower sear 1.hrelative to the bottom of housing 1.i; this angle is critical tomaintain lower sear 1.h at a parallel position to the bottom of housing1.i.

Also in FIG. 4, part 1.a is the pivot point for the claw 1.b and 1.t. isthe pivot point for the safety 1.k. The embodiment being describedherein utilizes an upward opening claw or string retaining means, thelower portion of this has a sear surface which when pulled back forcesthe keeper or holding sear portion out of the way allowing the bow to becocked. Sear engagement in the present embodiment is the amount the searsurfaces overlap at the 90-degree intersection. The lower sear portionis attached in this case to a trigger arm, which is pulled rearward toactivate the firing of the crossbow it is spring tensioned to always bein an engaged state. The sear in this case on the lower engaging seararea is a 0.125″ or ⅛″ dowel pin; we know the circumference is describedas 0.125″×3.14=0.3925″, if we divide this by 360 degrees we know thatthe round dowel sear when allowed to engage the preferred flat searsurface would do so on an area described as 0.001″ (one thousandth of aninch). The rotation of such a sear is achieved through the use of anoutward roller bearing on both the left and right hand side of the lowersear, this allows the upper sear when pushing back ward to move thedowel down and under it's spring biasing means returning back to itsposition to hold the sears in place ready for discharge. The rollingaction of the two bearings have an extremely efficient frictioncoefficient, coupled with a reduced contact area of 0.001″ of an inch onone sear surface allow for such a light trigger pull that effecting thetrigger pull to the required 3 lbs. or so can be adjusted through theuse of a spring pocket that has a threaded insert in it allowing varyingtension adjustment for the lower sear through the said spring biasingmeans. The spring tensioning allows the trigger geometry to stay thesame maintaining the integrity of the internal components, whilemaintaining optimal sear engagement at all times through a two contactpoint rolling sear surface.

Operation of the Preferred Embodiment

The trigger described above would be installed in a crossbow; to loadit, the user would place the crossbow on the ground supported by onefoot, usually in a stirrup. The user would then grab the string withleft and right hands and pull back on the crossbow string. The stringwould be pulled into opening 1.c and this rearward movement will causeclaw 1.b to move rearward, forcing lower sear 1.h to pivot about itpivot point 1.g; this movement will also cause pin 1.j to force safety1.k to pivot about 1.t, placing the safety into a safe position becauseit interferes with the rear portion of lower sear 1.h. The upper searsurface 1.f will come and engage against dowel pin 1.p, which ispreferably a 0.125″ diameter dowel pin. The crossbow is now ready toload an arrow for firing at a later time.

To fire the user will move safety 1.k into the fire (or unsafe) positionand depress the trigger 1.u which is rigidly attached to lower sear 1.h.This action will cause lower sear 1.h to pivot, allowing claw 1.b topivot upward, thus disengaging upper sear surface 1.f from dowel pin1.p, and fire the arrow.

While the foregoing written description of the invention enables one ofordinary skill to make and use what is considered presently to be thebest mode thereof, those of ordinary skill will understand andappreciate the existence of variations, combinations, and equivalents ofthe specific embodiment, method, and examples herein. The inventionshould therefore not be limited by the above described embodiment,method, and examples, but by all embodiments and methods within thescope and spirit of the invention. For example, embodiments of thisinvention can be used for any other devices that use a trigger, such asguns, rifles, pistols, slingshots, etc. Similarly, adapting a long rodor an arm to replace or to actuate the trigger 1.u of the embodimentsherein, could. enable the positioning of a trigger far from the action,such as in a bull pup configuration.

What is claimed as the invention is:
 1. A crossbow trigger mechanismcomprising: a) a housing adapted for installation in a crossbow stock;b) a forward-opening bowstring entry area in the upper portion of saidhousing for receiving a bowstring; c) a one-piece trigger pivotallyinstalled in a lower portion of said housing, said trigger comprising atrigger arm extending downwardly from the trigger pivot point and out ofthe case and a first sear having a first sear surface; d) a bowstringretaining claw connected to a second sear having a second sear surface;whereby, when a bowstring is retained by said bowstring-retaining clawthe first sear surface engages the second sear surface; whereby, whensaid trigger is pulled rearwardly, first sear surface disengages fromthe second sear surface, and, whereby by virtue of the force produced bybowstring tension, the bowstring retaining claw pivots upwardly awayfrom said bowstring entry area, thereby releasing said bowstring toproject an arrow or other projectile; whereby at least one of the firstsear surface and the second sear surface is a pivoting pin mounted onroller bearings.
 2. The crossbow trigger mechanism of claim 1, furthercomprising a manual safety lever having a safe position and a fireposition; an auto-safety pin whereby, when a bowstring is retained bysaid bowstring-retaining claw, said auto-safety pin moves said manualsafety lever to the safe position.